From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: "linux-perf-use." <linux-perf-users@vger.kernel.org>,
Wang Nan <wangnan0@huawei.com>
Subject: Re: perf segfault in docker container
Date: Fri, 10 Jun 2016 17:15:19 -0300 [thread overview]
Message-ID: <20160610201519.GE3826@kernel.org> (raw)
In-Reply-To: <CAE40pdfWpz6rreOCMJCs1P8WXfOXO_B5zZoeOyC_5usYGp8xRQ@mail.gmail.com>
Em Thu, Jun 09, 2016 at 02:14:11PM -0700, Brendan Gregg escreveu:
> G'Day,
>
> Default docker container, in Linux 4.7-rc2, with latest perf from perf/core:
>
> docker# ./perf record -F 99 -a
> Segmentation fault
>
> The segfault is in perf_event__synthesize_kernel_mmap(). I know
> symbol__read_kptr_restrict() has been updated recently to fix similar
> segfaults, hence getting perf/core.
>
> I think the problem is this:
>
> docker# id
> uid=0(root) gid=0(root) groups=0(root)
> docker# cat /proc/sys/kernel/kptr_restrict
> 1
>
> (I'd previously set "echo -1 > /proc/sys/kernel/perf_event_paranoid")
>
> The current (May 24) code has, symbol__read_kptr_restrict():
>
> if (fgets(line, sizeof(line), fp) != NULL)
> value = (geteuid() != 0) ?
> (atoi(line) != 0) :
> (atoi(line) == 2);
>
> assumes that if euid is 0 && kptr_restrict isn't 2, then we're aren't
> restricted. But we are. Maybe the code should check for CAP_SYS_ADMIN,
> instead of euid == 0?
Ack, reproduced will work on it. Thanks for the report.
- Arnaldo
prev parent reply other threads:[~2016-06-10 20:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-09 21:14 perf segfault in docker container Brendan Gregg
2016-06-10 10:28 ` Aravinda Prasad
2016-06-21 22:32 ` Brendan Gregg
2016-06-21 22:43 ` Brendan Gregg
2016-06-22 21:35 ` Aravinda Prasad
2016-06-10 20:15 ` Arnaldo Carvalho de Melo [this message]
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